scholarly journals Design of a hollow cathode thruster: concepts, parameter study and initial test results

2021 ◽  
Author(s):  
Norman Gondol ◽  
Martin Tajmar
Keyword(s):  
Tungsten Wire ◽  
Electric Propulsion ◽  
Plasma Discharge ◽  
Charge Carriers ◽  
Parameter Study ◽  
Test Results ◽  
Low Thrust ◽  
Hollow Cathodes ◽  
Thoriated Tungsten ◽  
Thrust Measurement

AbstractTwo electric propulsion concepts have been developed at Technische Universität Dresden as spin-off devices of regular hollow cathodes and initial testing has been conducted. Both devices represent millinewton thrusters that take advantage of thermionic electron emission using the low work function materials C12A7, LaB6, and thoriated tungsten in different design configurations. The first concept represents an electrothermal thruster which generates thrust by expanding and accelerating a heated propellant in a nozzle. Initial thrust measurement tests were carried out which showed thrust levels well above cold gas thrust, but low thrust efficiencies. The influence of different geometric parameters on the discharge properties and the performance is investigated and presented. The second thruster concept is a novel electromagnetic device in which charge carriers in a plasma discharge are accelerated by an applied magnetic field that is orthogonally oriented to the discharge current. Initial tests with C12A7 were not successful, but the functionality of the concept was shown by thrust measurements using a thoriated tungsten wire as an electron emitter.

scholarly journals Thrust measurement and thrust balance development at DLR’s electric propulsion test facility

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Andreas Neumann ◽  
Jens Simon ◽  
Jens Schmidt
Keyword(s):  
Electric Propulsion ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Space Mission ◽  
Measurement Range ◽  
Test Facility ◽  
Background Information ◽  
Low Thrust ◽  
Diagnostic Systems ◽  
Thrust Measurement

AbstractElectric space propulsion thrusters only produce low thrust forces. For the fulfillment of a space mission this implies long thruster runtimes, and this entails long qualification times on ground. For such long testing times, a ground facility requires a vacuum chamber and a powerful pumping system which can guarantee high vacuum over extended times and under thruster gas load. DLR’s STG-ET is such a ground test facility. It has a high pumping capability for the noble gases typically used as propellants. One basic diagnostic tool is a thrust measurement device, among various other diagnostic systems required for electric propulsion testing, e.g. beam diagnostics. At DLR we operate a thrust balance developed by the company AST with a thrust measurement range of 250 mN and capable of thruster weights up to 40 kg. Adversely, it is a bulky and heavy device and all upgrades and qualification work needs to be done in a large vacuum chamber. In order to have a smaller device at hand a second thrust stand is under development at DLR. The idea is to have a light and compact balance that could also be placed in one of the smaller DLR vacuum chambers. Furthermore, the calibration is more robust and the whole device is equipped with a watercooled housing. First tests are promising and showed a resolution well below 1 mN. In this paper we give background information about the chamber, describe the basics of thrust measurement and the development of a new balance.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

Resistive MHD modes in hollow cathodes external plasma

2021 ◽  
Author(s):  
Giulia Becatti ◽  
Francesco Burgalassi ◽  
Fabrizio Paganucci ◽  
Matteo Zuin ◽  
Dan M Goebel
Keyword(s):  
Magnetic Field ◽  
Hollow Cathode ◽  
Electric Propulsion ◽  
Axial Magnetic Field ◽  
Mhd Equations ◽  
Linear Perturbation ◽  
Plasma Parameters ◽  
Hollow Cathodes ◽  
Plume Region ◽  
Helical Mode

Abstract A significant number of plasma instabilities occur in the region just outside of hollow cathodes, depending on the injected gas flow, the current level and the application of an external magnetic field. In particular, the presence of an axial magnetic field induces a helical mode, affecting all the plasma parameters and the total current transported by the plasma. To explore the onset and behavior of this helical mode, the fluctuations in the plasma parameters in the current-carrying plume outside of a hollow cathode discharge have been investigated. The hollow cathode was operated at a current of 25 A, and at variable levels of propellant flow rate and applied magnetic fields. Electromagnetic probes were used to measure the electromagnetic fluctuations, and correlation analysis between each of the probe signals provided spatial-temporal characterization of the generated waves. Time-averaged plasma parameters, such as plasma potential and ion energy distribution function, were also collected in the near-cathode plume region by means of scanning emissive probe and retarding potential analyzer. The results show that the helical mode exists in the cathode plume at sufficiently high applied magnetic field, and is characterized by the presence of a finite electromagnetic component in the axial direction, detectable at discharge currents $\geq$ 25 A. A theoretical analysis of this mode reveals that one possible explanation is consistent with the hypotheses of resistive magnetohydrodynamics, which predicts the presence of helical modes in the forms of resistive kink. The analysis has been carried out by linear perturbation of the resistive MHD equations, from which it is possible to obtain the dispersion relation of the mode and find the $k-\omega$ unstable branch associated with the instability. These findings provided the basis for more detailed investigation of resistive MHD modes and their effect in the plume of hollow cathodes developed for electric propulsion application.

scholarly journals STG-ET: DLR electric propulsion test facility

2017 ◽  
Vol 3 ◽  
Author(s):  
Andreas Neumann
Keyword(s):  
Electric Propulsion ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Test Facility ◽  
Space Propulsion ◽  
Beam Dump ◽  
Pumping System ◽  
Thrust Measurement ◽  
Electric Space

DLR operates the High Vacuum Plume Test Facility Göttingen – Electric Thrusters (STG-ET). This electric propulsion test facility has now accumulated several years of EP-thruster testing experience. Special features tailored to electric space propulsion testing like a large vacuum chamber mounted on a low vibration foundation, a beam dump target with low sputtering, and a performant pumping system characterize this facility. The vacuum chamber is 12.2m long and has a diameter of 5m. With respect to accurate thruster testing, the design focus is on accurate thrust measurement, plume diagnostics, and plume interaction with spacecraft components. Electric propulsion thrusters have to run for thousands of hours, and with this the facility is prepared for long-term experiments. This paper gives an overview of the facility, and shows some details of the vacuum chamber, pumping system, diagnostics, and experiences with these components.

Recent progress in research and development of hollow cathodes for electric propulsion

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Dan R. Lev ◽  
Ioannis G. Mikellides ◽  
Daniela Pedrini ◽  
Dan M. Goebel ◽  
Benjamin A. Jorns ◽  
...  
Keyword(s):  
Research And Development ◽  
Electric Propulsion ◽  
Recent Progress ◽  
Hollow Cathodes

Experimental study of a low-thrust measurement system for thruster ground tests

2014 ◽  
Vol 85 (3) ◽  
pp. 035102 ◽  
Author(s):  
Jingsong Gong ◽  
Lingyun Hou ◽  
Wenhua Zhao
Keyword(s):  
Experimental Study ◽  
Measurement System ◽  
Low Thrust ◽  
Thrust Measurement

An Analysis of the Efficiency of Electric Propulsion Engines for Maintaining a Low Orbit of Small Spacecraft

2020 ◽  
pp. 65-74
Author(s):  
V.V. Volotsuev ◽  
V.V. Salmin
Keyword(s):  
Electric Propulsion ◽  
Aerodynamic Drag ◽  
Specific Impulse ◽  
Active Movement ◽  
Engine Fuel ◽  
Low Thrust ◽  
Atmospheric Density ◽  
Small Spacecraft ◽  
Drag Forces ◽  
Electric Engine

This paper examines the problem of maintaining the plane parameters of the working orbit of a small spacecraft using an electric propulsion engine. In low working orbits, due to the Earth’s atmosphere, a spacecraft is subjected to aerodynamic drag forces, which results in a decrease in the radius of the orbit and a potential termination of the useful target functioning. The time parameters of the cyclogram for maintaining the working orbit of a small spacecraft with an electric low thrust engine are analyzed taking into account the variability of the atmospheric density. The cyclogram consists of sections of the passive and active movement under the action of the low thrust engine. For the satellite under study, suitable thrust parameters of the electric engine are selected, which allow the correction of the plane parameters of the low orbit. Using the characteristics of the thrust and specific impulse of the electric jet engine, fuel reserves for correction over a long period of time are calculated. The results of the analysis confirm the effectiveness of the electric propulsion engine in terms of fuel consumption for correction.

scholarly journals Minimum-Fuel Planar Earth-to-Mars Low-Thrust Trajectories Using Bang-Bang Control

2021 ◽  
Author(s):  
Daero Lee
Keyword(s):  
Optimal Control ◽  
Boundary Value Problems ◽  
Electric Propulsion ◽  
Direct Method ◽  
Boundary Value ◽  
Specific Impulse ◽  
Direct Methods ◽  
Optimization Methods ◽  
Low Thrust ◽  
Primer Vector Theory

Recent advance in electric propulsion systems have demonstrated that these engines can be used for for long-duration interplanetary voyages. Constant specific impulse engine described as a thrust-limited engine is an example of this type of engine, processing the ability to operate at a constant level of impulse. The determination of minimum-fuel, planar heliocentric Earth-to-Mars low-thrust trajectories of spacecraft using a constant specific impulse is discussed considering the first-order necessary conditions derived from Lawden’s primer vector theory. The minimum-fuel low-thrust Earth-to-Mars optimization problem is then solved in two-dimensional, heliocentric frame using both indirect and direct methods. In the indirect method, two-point-boundary-value problems are derived to solve boundary value problems for ordinary differential equations. In the direct method, a general-purpose optimal control software called GPOPS-II is adopted to solve these optimal control problems. Numerical examples using two different optimization methods are presented to demonstrate the characteristics of minimum-fuel planar low-thrust trajectories with on-off-on thrust sequences at three chosen flight times and available maximum powers. The results are useful for broad trajectory search in the preliminary phase of mission designs.

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